The visual system has emerged as a premier model for understanding information processing by neurons. Within vision, the submodality of color provides a particularly attractive experimental platform: we know a tremendous amount about the phenomenology of color perception and can explain some aspects of color perception, quantitatively and with high precision, by well- understood physiological processes. As a result of this progress, we can quickly and accurately diagnose many distinct forms of color blindness and can build devices that render colors accurately. On the other hand, our understanding of the neurophysiology of color vision is largely restricted to the retina. The central mechanisms of color vision are largely unknown, and many aspects of color perception cannot be explained by retinal mechanisms. The proposed research is to measure the quality and behavioral relevance of the signals beyond the retina that mediate color vision. Two specific aims are planned: 1) Single neuron recording in the primary visual cortex to identify the neurons most likely to underlie color vision. 2) Single neuron recording in the primary visual cortex to study how manipulations that affect color appearance affect neuronal responses. The proposed experiments extend our knowledge of color vision toward an understanding of the principles of neuroscience that give rise to perception and its disorders. Such an understanding promises to provide the means to promote recovery of visual function following trauma or neurological disease.